Backside metal patterning die singulation system and related methods

ABSTRACT

Implementations of methods of singulating a plurality of die included in a substrate may include forming a plurality of die on a first side of a substrate, forming a backside metal layer on a second side of a substrate, applying a photoresist layer over the backside metal layer, patterning the photoresist layer along a die street of the substrate, and etching through the backside metal layer located in the die street of the substrate. The substrate may be exposed through the etch. The method may also include singulating the plurality of die included in the substrate through removing a substrate material in the die street.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Patent Application 62/796,659, entitled “BACKSIDE METALPATTERNING DIE SINGULATION SYSTEM AND RELATED METHODS” to Seddon, whichwas filed on Jan. 25, 2019, the disclosure of which is herebyincorporated entirely herein by reference.

BACKGROUND 1. Technical Field

Aspects of this document relate generally to die singulation systems andmethods. More specific implementations involve methods of singulatingsemiconductor die from a thinned substrate.

2. Background

Semiconductor devices include integrated circuits found in commonelectrical and electronic devices, such as phones, desktops, tablets,other computing devices, and other electronic devices. The devices areseparated through singulating a wafer of semiconducting material into aplurality of semiconductor die. Various layers may be coupled to thefront side and/or the backside of the wafer. Upon singulation, the diecan be mounted on a package and electrically integrated with the packagewhich may then be used in the electrical or electronic device.

SUMMARY

Implementations of methods of singulating a plurality of die included ina substrate may include forming a plurality of die on a first side of asubstrate, forming a backside metal layer on a second side of asubstrate, applying a photoresist layer over the backside metal layer,patterning the photoresist layer along a die street of the substrate,and etching through the backside metal layer located in the die streetof the substrate. The substrate may be exposed through the etch. Themethod may also include singulating the plurality of die included in thesubstrate through removing a substrate material in the die street.

Implementations of methods of singulating a plurality of die included ina substrate may include one, all, or any of the following:

The method may include thinning the second side of the substrate and thesubstrate may be thinned to less than 50 micrometers thick.

The method may include thinning the second side of the substrate and thesubstrate may be thinned to less than 30 micrometers thick.

The backside metal layer may be 10 micrometers thick.

Patterning the photoresist layer may include exposing the photoresistlayer and developing the photoresist layer.

Removing substrate material in the die street may include using either alaser beam or a saw blade.

The method may include remote plasma healing a plurality of sidewalls ofthe plurality of die after singulating the die.

Removing substrate material in the die street may include plasmaetching.

Singulating the plurality of die included in the substrate throughplasma etching may include removing a portion of the substrate materialof the substrate having a width less than a width of the die street.

Implementations of methods of singulating a plurality of die included ina substrate may include forming a plurality of die on a first side of asubstrate, forming a seed layer on a second side of a substrate oppositethe first side of the substrate, applying a photoresist layer over theseed layer, patterning the photoresist layer, forming a backside metallayer over the seed layer, removing the photoresist layer, andsingulating the plurality of die included in the substrate throughremoving a substrate material in the die street and through removing aseed layer material in the die street.

Implementations of methods of singulating a plurality of die included ina substrate may include one, all, or any of the following:

The seed layer may include titanium.

The backside metal layer may include copper.

Removing substrate material in the die street may include plasmaetching.

Removing substrate material in the die street and removing seed layermaterial in the die street may include using either a laser beam or asaw blade.

The method may include thinning the second side of the substrate to athickness less than 30 micrometers.

The method may include aligning the substrate from a backside of asubstrate.

Implementations of methods of singulating a plurality of die included ina substrate may include forming a plurality of die on a first side of asubstrate, thinning a second side of a substrate, forming a seed layeron a second side of a substrate opposite the first side of thesubstrate, applying a photoresist layer over the seed layer, patterningthe photoresist layer, forming a backside metal layer over the seedlayer, removing the photoresist layer, and singulating the plurality ofdie included in the substrate through removing substrate material in thedie street and through removing seed layer material in the die streetusing either a laser beam and a saw blade.

Implementations of methods of singulating a plurality of die included ina substrate may include one, all, or any of the following:

The method may include remote plasma healing a sidewall of the die.

The backside metal layer may be 10 micrometers thick.

The substrate may be thinned to less than 50 micrometers thick.

The foregoing and other aspects, features, and advantages will beapparent to those artisans of ordinary skill in the art from theDESCRIPTION and DRAWINGS, and from the CLAIMS.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations will hereinafter be described in conjunction with theappended drawings, where like designations denote like elements, and:

FIG. 1 is a cross sectional side view of a portion of a substrate;

FIG. 2 is a cross sectional side view of a plurality of layers coupledto a first side of the substrate of FIG. 1;

FIG. 3 is a view of the substrate and plurality of layers of FIG. 2 in aflipped orientation;

FIG. 4 is a view of the substrate and plurality of layers of FIG. 3 withthe substrate thinned;

FIG. 5 is a view of the thinned substrate and plurality of layers ofFIG. 4 with a backside metal layer coupled to the second side of thesubstrate;

FIG. 6 is a view of a photoresist layer formed over the backside metallayer of FIG. 4;

FIG. 7 is a view of the photoresist layer of FIG. 6 after patterning thephotoresist layer;

FIG. 8 is a view of the backside metal layer of FIG. 7 having a grooveformed entirely therethrough;

FIG. 9 is a view of the substrate of FIG. 8 singulated into a pluralityof die;

FIG. 10 is a cross-sectional side view of a portion of a substrate witha seed layer coupled thereto;

FIG. 11 is a cross-sectional side view of a photoresist layer formedover the seed layer of FIG. 10;

FIG. 12 is a view of the photoresist layer of FIG. 11 after thephotoresist layer has been patterned;

FIG. 13 is a cross-sectional side view of a backside metal layer formedover the seed layer of FIG. 12;

FIG. 14 is a view of the substrate and seed layer of FIG. 13 with thephotoresist layer removed;

FIG. 15 is a view of the substrate of FIG. 14 singulated into aplurality of die;

FIG. 16 is a view of the plurality of die of FIG. 15 having smoothsidewalls;

FIG. 17 is a view of the substrate of FIG. 14 in a flipped orientationand with substrate material in the die street removed; and

FIG. 18 is a view of the substrate of FIG. 14 singulated into aplurality of die.

DESCRIPTION

This disclosure, its aspects and implementations, are not limited to thespecific components, assembly procedures or method elements disclosedherein. Many additional components, assembly procedures and/or methodelements known in the art consistent with the intended die singulationsystems and related methods will become apparent for use with particularimplementations from this disclosure. Accordingly, for example, althoughparticular implementations are disclosed, such implementations andimplementing components may comprise any shape, size, style, type,model, version, measurement, concentration, material, quantity, methodelement, step, and/or the like as is known in the art for such diesingulation systems and related methods, and implementing components andmethods, consistent with the intended operation and methods.

Referring to FIG. 1, a cross sectional side view of a portion of asubstrate 2 is illustrated. The term “substrate” refers to asemiconductor substrate as a semiconductor substrate is a common type ofsubstrate, however, “substrate” is not an exclusive term that is used torefer to all semiconductor substrate types. Similarly, the term“substrate,” may refer to a wafer as a wafer is a common type ofsubstrate, however, “substrate” is not an exclusive term that is used torefer to all wafers. The various semiconductor substrate types disclosedin this document that may be utilized in various implementations may be,by non-limiting example, round, rounded, square, rectangular, or anyother closed shape. In various implementations, the substrate 2 mayinclude a substrate material such as, by non-limiting example, singlecrystal silicon, silicon dioxide, glass, gallium arsenide, sapphire,ruby, silicon-on-insulator, silicon carbide, polycrystalline oramorphous forms of any of the foregoing, and any other substratematerial useful for constructing semiconductor devices. In particularimplementations, the substrate may be a silicon-on-insulator substrate.

Referring to FIG. 2, a cross sectional side view of a plurality oflayers coupled to a first side of the substrate of FIG. 1 isillustrated. In various implementations, before singulating a pluralityof die from the substrate 2, the method of forming a plurality of diemay include forming a plurality of die on the substrate. This mayinclude forming a plurality of layers 4 on a first side 6 the substrate2. As illustrated by FIG. 2, the plurality of layers 4 may be patterned,and in various implementations, may be patterned (or otherwise removed)to not be over a die street 8 in the substrate 2. The plurality oflayers may include, by non-limiting example, one or more metal layers,one or more passivation layers, any other layer, and any combinationthereof. In various implementations passivation layers may include, bynon-limiting example, silicon nitride, oxides, metal electrical teststructures, electrical test pads, silicon dioxide, polyimides, metalpads, residual underbump metallization (UBM), any combination thereof,and any other layer or material capable of facilitating electrical orthermal connection between the one or more semiconductor die and/orprotecting the one or more semiconductor die from contaminants. Invarious implementations, the plurality of die may include powersemiconductor devices, such as, by non-limiting example, a MOSFET, anIGBT, or any other power semiconductor device. In other implementations,the plurality of die may include non-power semiconductor devices.

Referring to FIG. 3, a view of the substrate and plurality of layers ofFIG. 2 in a flipped orientation is illustrated. The method of formingand singulating a plurality of die includes flipping the substrate and,though not illustrated, in various implementations, the method mayinclude applying a tape to a first side 10 of the plurality of layers 4.Such a tape may be a backgrind tape in various implementations.Referring to FIG. 4, a view of substrate and plurality of layers of FIG.3 with the substrate thinned is illustrated. In various implementations,the method of forming and singulating a plurality of die may includethinning the second side 12 of the substrate 2. In variousimplementations, the substrate 2 may be thinned to a thickness less than50 micrometers (μm). In other implementations, the substrate 2 may bethinned to a thickness less than 30 μm. In still other implementations,the substrate 2 may be thinned to a thickness less than 100 μm, morethan 100 μm, and in other various implementations, the substrate 2 maynot be thinned. In particular implementations, the substrate 2 may bethinned to a thickness of about 25 μm, and in other particularimplementations, the substrate may be thinned to a thickness of about 75μm. The substrate 2 may be thinned through backgrinding, etching, or anyother thinning technique. In particular implementations, the substrateis thinned using a backgrinding process marketed under the trade nameTAIKO by DISCO of Tokyo, Japan to form an edge ring used to support thethinned substrate.

Referring to FIG. 5, a view of thinned substrate and plurality of layersof FIG. 4 with a backside metal layer coupled to the second side of thesubstrate is illustrated. The method of forming a plurality of die andsingulating the plurality of die includes forming a backside metal layer14 on the second side 12 of the substrate 2. In particularimplementations, the backside metal layer 14 may be copper or a copperalloy. In other implementations, the backside metal layer may includeany other type of metal, alloy thereof, or combination thereof. Invarious implementations, the backside metal layer 14 may be about 10 μmthick. In other implementations, the backside metal layer may be more orless thick than 10 μm, and in particular implementations, the backsidemetal layer 14 may be about 15 μm thick. The backside metal layer 14 maybe evaporated onto the substrate 2, however, in other implementations(including implementations having thicker substrates and/or thickerbackside metal layers), the backside metal layer 14 may be plated ontothe substrate 2 or formed on the substrate using another technique. Invarious implementations, the backside metal layer 14 may be formed overthe entire second side 12 of the substrate 2. In such implementations,the backside metal layer 14 may strengthen the substrate 2.

Referring to FIG. 6, a view of a photoresist layer formed over thebackside metal layer of FIG. 4 is illustrated. The method of forming aplurality of die and singulating the plurality of die may includeapplying a photoresist layer 18 over the backside metal layer 14, and invarious implementations, over the entire second side 16 of the backsidemetal layer 14. In various implementations, the photoresist layer 18 maybe directly coupled to the second side 16 (opposite the first side 20)of the backside metal layer 14. In various implementations, the methodmay include applying the photoresist layer 18 through spin coating orspraying the photoresist layer 18 onto the backside metal layer 14. Invarious implementations, the photoresist layer 18 may be about 1 μmthick, however, in other implementations the photoresist layer may beless than or more than 1 μm thick.

Prior to patterning the photoresist layer 18, the method of singulatingthe plurality of die in the substrate may include aligning thesubstrate. In various implementations, the method may include aligningthe substrate from the first side (which may be the front side, orbottom side as oriented in FIG. 6) using optics or a camera. In suchimplementations, the optics or camera may be placed below the substrateand may detect a plurality of alignment features formed on or within thesubstrate. In various implementations, the alignment features may beformed on or within the die street 8 of the substrate. Inimplementations having tape coupled to the first side 10 of theplurality of layers, the optics or camera may be configured to detectthe plurality of alignment features through the tape. In a particularimplementation, the substrate may be aligned using an infrared (IR)camera and IR alignment features. In other implementations, thesubstrate may be aligned from the backside, or second side 12 of thesubstrate. In such implementations, alignment features may be placed onthe polymer layer 18 covering the backside metal layer 14. Such featuresmay be placed according to corresponding alignment features on the frontside of the substrate. In other implementations where the substrateincludes a ring around the perimeter after thinning the substrate, themethod of aligning the substrate may include placing alignment featuresin the periphery of the substrate and grinding down the perimeter ring.The substrate may then be aligned from the backside, or second side 12of the substrate by using the alignment features along the outer edge ofthe device. Such an alignment method may include using IR spectroscopy.

Referring to FIG. 7, a view of the photoresist layer of FIG. 6 afterpatterning the photoresist layer is illustrated. The method ofsingulating a plurality of die from the substrate 2 includes patterningthe photoresist layer 18 along the die street 8 of the substrate. Thephotoresist layer may be made of a positive or negative photosensitivematerial (positive or negative photoresist). In various implementations,patterning the photoresist layer 18 may include exposing a positivephotoresist along the die streets 8 of the substrate 2. In otherimplementations, patterning the photoresist layer 18 may includeexposing the portions of the photoresist layer not along a die street ina negative photoresist. In various implementations, a single maskincluding the pattern of all of the die streets 8 may be used inexposing the positive photoresist layer. In other implementations,multiple masks may be used to expose the positive photoresist layeralong the die streets 8 or along the portions of the photoresist layernot over the die streets 8. In such implementations, the substrate maybe stepped or scanned below the pattern to duplicate the pattern acrossthe substrate. Patterning the photoresist layer 18 also includesdeveloping the photoresist layer 18 to remove the portions of thephotoresist layer over the die streets 8. In various implementationswhere a plasma etch is used to singulate the plurality of die, asdisclosed later herein, the patterns of the die streets formed in thephotoresist layer may include a variety of shapes, including, bynon-limiting example, quadrilateral, rectangular, rounded rectangular,circular, ovate, triangular, pentagonal, hexagonal, heptagonal,octagonal, or any other closed shape. Because plasma etching may be usedto singulated the plurality of die, the die streets need not be straightperpendicularly aligned lines extending across the entire substrate.

Referring to FIG. 8, a view of the backside metal layer of FIG. 7 havinga groove formed entirely therethrough is illustrated. In variousimplementations, the method of singulating a plurality of die mayinclude etching through the backside metal layer 14 located in the diestreet 8 of the substrate 2. Etching, as illustrated by FIG. 8, may forma groove 20 through the backside metal layer 14 and may expose thesubstrate 2 through the etch. In various implementations, the etchapplied within the groove 24 may be a wet etch and may be sprayed intothe groove 24. In other implementations the wet etch may be appliedusing a method aside from spraying. In various implementations, thoughnot illustrated, tape or other layer may be applied to the front side,or outer surface 30 of the plurality of layers 4. The tape or otherlayer may protect the pads 62 of the plurality of die from the etch.Because of the precision of patterning the photoresist layer 18, invarious implementations, the groove 20 formed within the die street 8may also precisely (at least to the level of precision of the patterningof the photoresist layer) correspond to the die street 8. In turn, morenarrow die streets than those is in saw singulation may be utilized aspatterning of the photoresist layer 18 more closely matches the diestreets 8. The more narrow die streets may ultimately result in moredies per substrate.

Referring to FIG. 9, a view of the substrate of FIG. 8 singulated into aplurality of die is illustrated. In various implementations, and asillustrated by FIG. 9, the method of singulating a plurality of die in asubstrate includes removing the photoresist layer 18. In variousimplementations, the photoresist layer 18 may be removed through, bynon-limiting example, a plasma ashing process or with a solvent stripprocess.

In various implementations, the method of singulating a plurality of dieincludes singulating a plurality of die 32 through removing thesubstrate material of the substrate 2 in the die street 8. The substratematerial may be removed through plasma etching at the portion of thesubstrate 2 exposed by the etching. In various implementations, a plasmaetch process marketed under the tradename BOSCH® by Robert Bosch GmbH,Stuttgart Germany (the “Bosch process”), may be used to singulate thesubstrate 2 into a plurality of die 32. In other implementations, otherplasma etch processes may be used to singulate the plurality of die 32from the substrate 2. In various implementations, the die singulated mayinclude a perimeter which may be, by non-limiting example,quadrilateral, rectangular, rounded rectangular, circular, ovate,triangular, pentagonal, hexagonal, heptagonal, octagonal, or any otherclosed shape. In various implementations, though not illustrated,singulating the plurality of die included in the substrate throughplasma etching may include removing a portion of the substrate materialof the substrate having a width less than a width of the die street, orgroove. In such implementations, the width of the removed portion fromplasma etching is less than the width of the die street as plasma diesingulation is capable of creating a die street more narrow than a diestreet created through sawing. In other implementations, and asillustrated by FIG. 9, the width of the portion of the substrate removedthrough the plasma etch may be the same as the width of the die streetby singulating the plurality of die 32 through removing through plasmaetch all of the substrate material of the substrate 2 in the die street8.

In other implementations, the plurality of die may be singulated byremoving the substrate material in the die street using either a laserbeam or a saw blade. In such implementations, the laser beam or sawblade may result in roughened sidewalls of the die street (or roughenedsidewalls of the plurality of die). In such implementations, the methodof singulating a plurality of die from the substrate may include remoteplasma healing a sidewall of each die (or sidewall of the die street) ofthe plurality of die. In such implementations, an isotropic plasma etchmay be applied to the sidewalls of the die street, or the sidewalls ofthe plurality of die. The plasma may penetrate/facilitate reaction withthe materials of the cracks and/or chips of the sidewalls formed whenthe plurality of die were singulated from the substrate. As the plasmaenters the cracks and/or chips, the damaged portion of the substrate mayetch away and result in smoothed, or healed, sidewalls of the diestreet.

Though not illustrated, in various implementations using a laser beam orsaw blade to singulate a plurality of die, the method of singulating aplurality of die from a substrate may include depositing a diffusionbarrier layer between the backside metal layer and the substrate. Insuch implementations, the diffusion barrier layer may serve as an etchstop when the portion of the backside metal layer in the die street isetched. The diffusion barrier layer may also prevent migration of thebackside metal layer into the substrate during the etch. Inimplementations having a diffusion barrier layer, the portion of thediffusion barrier layer in the die street may be removed using a laserbeam or a saw blade and may be removed simultaneously with the substratematerial in the die street removed by the laser beam or the saw blade.In such implementations, the method of singulating a plurality of diefrom a substrate may include removing substrate material of thesubstrate in the die street using any method of removing substratematerial disclosed herein.

In the various implementations disclosed herein, by removing thebackside metal layer in the die street, the risk of re-deposition of thebackside metal material along the sidewalls of each die of the pluralityof die is reduced. Further, because various implementations disclosedherein include methods of singulating a plurality of die from a secondside, or backside of the substrate, there is no need to flip thesubstrate over in order to singulate the substrate from the first side,or side having the plurality of die formed thereon. The ability tosingulate the die from the backside may reduce damage to the substrate,and especially a thinned substrate, as it requires the substrate to behandled less and may thereby increase the die yield.

Referring to FIG. 10, a cross-sectional side view of a portion of asubstrate with a seed layer coupled thereto is illustrated. In variousimplementations, a method of singulating a plurality of die may includeforming a seed layer 38 on a second side 40 of a substrate 42 oppositethe first side 44 of the substrate. The substrate 42 may be any type ofsubstrate disclosed herein and may be formed and/or thinned using anymethod disclosed herein. Similarly, a plurality of die, which mayinclude a plurality of layers 46, may be formed on the first side 44 ofthe substrate 42 using any method disclosed herein. The plurality of diemay be any type of die disclosed herein. In particular implementations,the seed layer 38 may be directly coupled to the second side 40 of thesubstrate 42. The seed layer 38 may be sprayed onto the substrate 42 orapplied to the substrate using, by non-limiting example, electroplating,electroless plating, or another method of metal deposition. In variousimplementations, the seed layer may entirely coat the second side 40 ofthe substrate 42. In such implementations, the seed layer may provideelectrical continuity throughout the seed layer to facilitateelectroplating of a backside metal layer to the seed layer 38, asdisclosed later herein. In various implementations, the seed layer 38may include an adhesion layer which may be directly coupled to thesubstrate 42. The adhesion layer may include, by non-limiting example,titanium, tungsten, any other metal, any alloys thereof, and anycombination thereof. The seed layer 38 may also include a layer over theadhesion layer which may include the same material as the backside metallayer configured to be coupled to the seed layer. In variousimplementations, the layer of the seed layer 38 over the adhesion layermay include copper, any other metal, any alloy thereof, and anycombination thereof. In various implementations, the seed layer may beabout 1 μm thick, however, in other implementations the seed layer maybe more or less than 1 μm thick.

Referring to FIG. 11, a cross-sectional side view of a photoresist layerformed over the seed layer of FIG. 10 is illustrated. In variousimplementations, the method of singulating a plurality of die from thesubstrate 42 includes applying a photoresist layer 46 over the seedlayer 38. The photoresist layer 46 may be directly coupled to the seedlayer 38. The photoresist layer may be made of a positive photoresist ora negative photoresist. In particular implementations, the methodincludes spraying the photoresist layer 46 over and/or onto the seedlayer 38 though other coating techniques like spin coating may be usedin various implementations.

Upon applying the photoresist layer 46, the method of singulating theplurality of die in the substrate may include aligning the substrate. Invarious implementations, the method may include aligning the substratefrom the first side (which may be the front side, or bottom side asoriented in FIG. 11) using optics or a camera. In such implementations,the optics or camera may be placed below the substrate and may detect aplurality of alignment features formed on or within the substrate. Invarious implementations, the alignment features may be formed on orwithin the die street 48 of the substrate. In implementations havingtape coupled to the first side 50 of the plurality of layers 52, theoptics or camera may be configured to detect the plurality of alignmentfeatures through the tape. In a particular implementation, the substratemay be aligned using an infrared (IR) camera and IR alignment features.In other implementations, the substrate 42 may be aligned from thebackside, or second side 40 of the substrate. In such implementations,alignment features may be placed on the photoresist layer 46 coveringthe substrate 42. Such features may be placed according to correspondingalignment features on the front side of the substrate. In otherimplementations where the substrate includes a ring around the perimeterafter thinning the substrate, the method of aligning the substrate mayinclude placing alignment features in the periphery of the substrate andgrinding down the perimeter ring. The substrate may then be aligned fromthe backside, or second side 40 of the substrate by using the alignmentfeatures along the outer edge of the device. Such an alignment methodmay include using IR spectroscopy.

Referring to FIG. 12, a view of the photoresist layer of FIG. 11 afterthe photoresist layer has been patterned is illustrated. In variousimplementations, the method of singulating a plurality of die of asubstrate 42 includes patterning the photoresist layer 46 along the diestreet 48 of the substrate 42 resulting in the photoresist layercovering the die streets but not covering the rest of the seed layer 38between the die streets (or above the rest of the die). In variousimplementations, patterning the photoresist layer 46 may includeexposing a negative photoresist layer along the die streets 48 of thesubstrate 42. In other implementations, patterning the photoresist layer46 may include exposing the portions not along a die street of apositive photoresist layer. In various implementations, a mask with apattern corresponding to all of the die streets 48 may be used inexposing the positive photoresist layer. In other implementations,multiple masks may be used to expose the positive photoresist layeralong the die streets 48 or along the portions of the photoresist layernot over the die streets 48 using stepping or scanning operations.

In particular implementations may include exposing the entirelyphotoresist layer using a mask having a plurality of parallel slitstherein. After exposing the photoresist layer using the mask in a firstdirection, the mask may then be rotated 90 degrees (or more or less than90 degrees) and the photoresist layer may be exposed using the mask in asecond direction. Such an implementation may be used when the diesingulated are rectangular or have a quadrilateral shape. In a similarimplementation, the mask having the plurality of parallel slits may berotated a second time and the photoresist layer may be exposed a thirdtime. Such an implementation may be used when the die singulated aretriangular or another closed polygonal shape where more than two masksmay be employed and more than a single exposure step may be used toexpose the photoresist. Patterning the photoresist layer 46 alsoincludes developing the photoresist layer 46 to remove the portions ofthe photoresist layer not included in the die streets 48. Because thephotoresist layer is exposed and developed, the patterned photoresistlayer may correspond to the die streets with a high degree of accuracy.In turn, this may allow for accurate deposition of the backside metallayer, as disclosed later herein, and may also allow for more narrow diestreets, resulting in more die per substrate. In other implementations,and as illustrated by FIG. 12, the photoresist layer 46 is patternedwider than the die street 48.

Referring to FIG. 13, a cross-sectional side view of a backside metallayer formed over the seed layer of FIG. 12 is illustrated. In variousimplementations, the method of singulating a plurality of die includesforming a backside metal layer 54 over the seed layer 38 and between theopening in the photoresist layer. In particular implementations, themethod may include electroplating or electroless plating the backsidemetal layer 54 over the seed layer. The backside metal layer may includecopper, a copper alloy, any other metal, or any combination thereof. Thebackside metal layer 54 may be 10 μm thick, 15 μm thick, more than 10 μmthick, or less than 15 μm thick.

Referring to FIG. 14, a view of the substrate and seed layer of FIG. 13with the photoresist layer removed is illustrated. The method ofsingulating a plurality of die included in a substrate includes removingthe photoresist layer covering the die streets, as illustrated by FIG.13. The method may include removing the photoresist layer 46 throughetching, ashing, or solvent stripping. The seed layer 38 may preventdamage to the substrate 42 during removal of the photoresist layer 46.Upon removing the photoresist layer 46, the portion 56 of the seed layer38 in the die street 48 may be exposed.

Referring to FIG. 15, a view of the substrate of FIG. 14 singulated intoa plurality of die is illustrated. In various implementations, the dieof the plurality of die may include a quadrilateral perimeter or atriangular perimeter or other perimeter shape disclosed herein. Themethod of singulating a plurality of die 58 in the substrate 42 includesremoving substrate material in the die street 48 and removing the seedlayer material in the die street. In various implementations, thesubstrate material in the die street 48 and the seed layer material 38in the die street may be removed using either a laser beam or a sawblade. In such implementations, the seed layer material in the diestreet 48 may be simultaneously removed with the substrate material inthe die street as the laser ablation or sawing used to clear the seedmetal material from the die street may also clear the substrate materialfrom the die street. In implementations using a laser beam or saw bladeto singulate the plurality of die 58, the laser beam or saw blade mayresult in roughened sidewalls 60 of the die street 48 or of theplurality of die 58. In such implementations, the method of singulatinga plurality of die 52 from the substrate may include remote plasmahealing a sidewall of each die (or sidewall 60 of the die street 48) ofthe plurality of die 58. Referring to FIG. 16 a view of the plurality ofdie of FIG. 15 having smooth sidewalls is illustrated. In variousimplementations, the method of singulating the plurality of die 58 mayinclude removing damage from a sidewall 60 of the die street 48 throughremote plasma healing. In such implementations, an isotropic plasma etchmay be applied to the sidewalls 60 of the die street 48. The plasma maypenetrate/facilitate reaction with the materials of the cracks and/orchips of the sidewalls 60 formed when the plurality of die 58 weresingulated from the substrate 42. As the plasma enters the cracks and/orchips, the damaged portion of the substrate 42 may etch away and resultin smoothed, or healed, sidewalls 60 of the die street 48, asillustrated by FIG. 16.

In the various implementations disclosed herein, by removing thebackside metal layer in the die street, the risk of re-deposition of thebackside metal material along the sidewalls of each die of the pluralityof die is reduced. Though the seed metal layer may be removed at thesame time the substrate material is removed from the die street, and inturn, the plurality of die are singulated, because the seed metal layeris extremely thin as compared to the thickness of the backside metallayer, the risk of re-deposition is still reduced. Further, becausevarious implementations disclosed herein include methods of singulatinga plurality of die from a second side, or backside of the substrate,there is no need to flip the substrate over in order to singulate thesubstrate from the first side, or side having the plurality of dieformed thereon. The ability to singulate the die from the backside mayreduce damage to the substrate, and especially a thinned substrate, asit requires the substrate to be handled less.

Referring to FIG. 17, a view of the substrate of FIG. 14 in a flippedorientation and with substrate material in the die street removed isillustrated. In another implementation, rather than singulating theplurality of die as illustrated by FIG. 15, the method of singulating aplurality of die may include flipping the substrate 180 degrees andremoving the substrate material in the die street 48. In variousimplementations, the substrate material may be removed through plasmaetching, including any plasma etching process disclosed herein.Referring to FIG. 18, a view of the substrate of FIG. 14 singulated intoa plurality of die is illustrated. In various implementations, themethod of singulating a plurality of die 58 may include jet ablating theseed metal material in the die street 48. In the implementationillustrated by FIGS. 17-18, by removing the backside metal layer in thedie street and by removing the substrate material in the die streetthrough plasma etching prior to removing the seed layer material in thedie street 48, the risk of re-deposition of the backside metal materialalong the sidewalls of each die of the plurality of die may be removed.

In places where the description above refers to particularimplementations of die singulation systems and related methods andimplementing components, sub-components, methods and sub-methods, itshould be readily apparent that a number of modifications may be madewithout departing from the spirit thereof and that theseimplementations, implementing components, sub-components, methods andsub-methods may be applied to other die singulation systems and relatedmethods.

What is claimed is:
 1. A method of singulating a plurality of diecomprised in a substrate, the method comprising: forming a plurality ofdie on a first side of a substrate; forming a backside metal layer on asecond side of the substrate; applying a photoresist layer over thebackside metal layer; patterning the photoresist layer along a diestreet of the substrate; etching through the backside metal layerlocated in the die street of the substrate, wherein the substrate isexposed through the etch; and singulating the plurality of die comprisedin the substrate through removing substrate material in the die street.2. The method of claim 1, further comprising thinning the second side ofthe substrate, wherein the substrate is thinned to less than 50micrometers thick.
 3. The method of claim 1, further comprising thinningthe second side of the substrate, wherein the substrate is thinned toless than 30 micrometers thick.
 4. The method of claim 1, wherein thebackside metal layer is 10 micrometers thick.
 5. The method of claim 1,wherein patterning the photoresist layer further comprises exposing thephotoresist layer and developing the photoresist layer.
 6. The method ofclaim 1, wherein removing substrate material in the die street furthercomprises using one of a laser beam or a saw blade.
 7. The method ofclaim 6, further comprising remote plasma healing a plurality ofsidewalls of the plurality of die after singulating the plurality ofdie.
 8. The method of claim 1, wherein removing substrate material inthe die street further comprises plasma etching.
 9. The method of claim8, wherein singulating the plurality of die comprised in the substratethrough plasma etching further comprises removing a portion of thesubstrate material of the substrate having a width less than a width ofthe die street.
 10. A method of singulating a plurality of die comprisedin a substrate, the method comprising: forming a plurality of die on afirst side of a substrate; forming a seed layer on a second side of thesubstrate opposite the first side of the substrate; applying aphotoresist layer over the seed layer; patterning the photoresist layer;forming a backside metal layer over the seed layer; removing thephotoresist layer; and singulating the plurality of die comprised in thesubstrate through removing substrate material in a die street andthrough removing the seed layer material in the die street.
 11. Themethod of claim 10, wherein the seed layer comprises titanium.
 12. Themethod of claim 10, wherein the backside metal layer comprises copper.13. The method of claim 10, wherein removing substrate material in thedie street further comprises plasma etching.
 14. The method of claim 10,wherein removing substrate material in the die street and removing seedlayer material in the die street further comprises using one of a laserbeam or a saw blade.
 15. The method of claim 10, further comprisingthinning the second side of the substrate to a thickness less than 30micrometers.
 16. The method of claim 10, further comprising aligning thesubstrate from a backside of the substrate.
 17. A method of singulatinga plurality of die comprised in a substrate, the method comprising:forming a plurality of die on a first side of a substrate; forming aseed layer on the second side of a substrate opposite the first side ofthe substrate; applying a photoresist layer over the seed layer;patterning the photoresist layer; forming a backside metal layer overthe seed layer; removing the photoresist layer; singulating theplurality of die comprised in the substrate through removing substratematerial in a die street and through removing seed layer material in thedie street using one of a laser beam and a saw blade.
 18. The method ofclaim 17, further comprising remote plasma healing a sidewall of theplurality of die.
 19. The method of claim 17, wherein the backside metallayer is 10 micrometers thick.
 20. The method of claim 17, furthercomprising thinning the second side of the substrate, wherein thesubstrate is thinned to less than 50 micrometers thick.